Electrical control device



June 29, 1948. E. :5. DE MOTT 2,444,398

ELECTRICAL CONTROL DEVICE Filed June 21, 1946 ZZZW 46 39 J5 1a 36 1.9 i J? 4/ E fl 1& 8/ 51 52? To Confrzfl/ed 2 Device 53 awe/WM:

Patented June 29,1948

ELECTRICAL CONTROL DEVICE Elmer G. De Mott, Elizabeth, N. 1., aaaignor to Weston Electrical Instrument Corporation,

Newark,- N. 1., a corporation of New, Jersey Application June 21, 1946, Serial No. 678,234

11 Claims. (Cl. 175-820) This invention relates to relay apparatus and in particular to instrument type relays which control a load circuit in a desired manner in accordance with variation of the control current applied to the moving system of the instrument.

There are many different types of electrical apparatus which require that the power circuit thereto be controlled in accordance with variation of a related control current between predetermined upper and lower limits. As an example it may be required that the power circuit to the apparatus be closed when the control current reaches the predetermined low value and remain closed until the current has reached the predetermined high limit, or vice versa. Thus in an electric furnace having a thermo couple type of heat regulator, the minute current output of the thermo couple may be applied to the moving system of an instrument type relay so that as the temperature of the furnace fails below the selected operating point, one set of contacts are closed within the instrument which effects a closure of the furnace power supply circuit. As the furnace heat increases, the current output of the thermo couple increases causing the moving system of the instrument to close another set of contacts which eifects an opening of the power circuit.

When using instrument type relays having magnetized contacts that require separation by means additional to the reverse torque of the instrument's moving system, the control has been found very reliable. Relay apparatus of this type may be found described in U. 8. Patents Nos. 2,014,385; 2,014,386 and 2,014,387 issued September 17, 1935 to Anthony H. Lamb.

Each of these patents disclose a high-low control in which the load circuit is opened or closed as the control current through the instrument reaches predetermined high and low limits.

It is the general object of this invention to provide a simple, compact and relatively inexpensive arrangement for resetting the contacts of an instrument relay of the magnetic contact type.

Amore specific object is to provide a highiow-relay apparatus of the general type described which comprises alternately energized solenoids that actuate pusher means for resetting the high and low instrument contacts, and a transfer switch actuated in timed relation to operation of the solenoids to deenergize each of the latter after it has performed its contact resetting function and also to simultaneously ready the energizing circuit to the other solenoid.

Another specific object is to provide a pair of instrument relays of the magnetized contact type that are used to provide on" and "01! control of a load circuit in accordance with variation in control current applied to the moving system of each relay between predetermined high and low limits, the contact resetting or separating means for the instruments being actuated by solenoids that are alternately energized to perform their function, and which are immediately thereafter deenergized by means of a transfer switch which operates in timed relation to the separation of the contacts to open the circuit to the last ener- Biz-ed solenoid and to close a switch in the energizing circuit of the solenoid next to be energized by one of the sets of relay contacts.

Still another specific object is to provide an instrument relay of the magnetized contact type having one contact movable between a pair of stationary contacts, and a pair of solenoids for resetting or separating the contacts subsequent to their engagement, the circuit to each solenoid being controlled through the contacts of the instrument and also through contacts on a transfer switch which functions to deenergize each solenoid after it has performed its contact separating function and also to open and close the load circuit by means of contacts placed on the switch.

The foregoing and other objects and advantages of the invention will become more apparent from the following description when considered with the accompanying drawings in which preferred embodiments are shown.

Fig. 1 is a diagrammatic view of a relay instrument incorporating the invention having separate pointers which are magnetically attractive to corresponding high" and low" stationary contacts. Each of these pointers is provided with a solenoid operated contact reset mechanism that is actuated when the other pointer engages its stationary contact, and a transfer switch is commonly operated by both reset mechanisms to obtain the desired reset sequence and solenoid deenergization;

Fig. 2 shows a modified arrangement of basically the same construction but using separate relay instruments, the necessary operating interrelationship between the reset mechanisms of the two instruments being obtained by an external relay which also controls the load circuit; and

Figs. 3 and 4 show still other modified forms of the invention wherein the instrument relay contains but a single moving system including.

a pointer carried contact movable between "low" and high stationary contacts.

Referring now to Fig. l, the relay includes a case I which houses a pair of instrument mechanisms 2 and l. The left instrument mechanism I or "low relay, as. it is designated on the drawing, comprises a moving coil 4 that carries an electrically conductive pointer or contactor arm I on which a small iron rider I is nxed. Rider I constitutes the movable contact of the instrument and cooperates with a stationary, magnetized contact I that is made in the form of a small permanent magnet. Coil 4 may be connected, for example, across a control device (not shown) such as a thermocouple, photoelectric cell or some other device having a small but variable current output upon which the control is based. A permanent magnetic field is set up by a horseshoe type of magnet, only the poles I, of

which are shown. Hence as control current through coil 4 increases, pointer I will sweep clockwise in proportion to the magnitude of this current. Fig. 1 shows magnet contact I so placed in the sweep path of pointer I that the iron rider I will be drawn into engagement with contact I at a selected and relatively low magnitude of current in coil 4. The magnetic force holding rider 6 to contact I is greater than any torque developed by coil 4.

In order to reset" the pointer I, a pusher arm I in the form of a bell crank lever is supported on the casing I for rotation around pivot II, the arm I moving in a plane adjacent to and parallel with the plane in which pointer I moves. One end of lever 9 terminates in a pin II which projects into the path of movement of pointer I and is adapted to push against the pointer and reset" it by moving it Just outside of the field of magnetic attraction between contact I and rider I. The other end I2 of lever I is adapted to be acted upon by the armature II of a solenoid I4 when its coil II is energized. Thus as armature I3 is pulled up, lever I is rotated counter clockwise through a small distance to reset contactor arm I.

The parts in the right instrument mechanism 3 or "high" relay as it is designated on the drawing have the same construction as those in instrument mechanism I and hence will not be described in detail. However, corresponding parts of the two instrument mechanisms have been given the same reference numerals but with primes added to the numerals on mechanism 3 for identification purposes. It is to be noted that magnet contact I is so placed in the sweep path such that when "low contact is made, the pointer arm I' of the high" instrument mechanism is reset, and vice versa. l' or performing this function, the relay instrument is provided with a transfer switch mechanism II that includes a contactor arm I! mounted for movement about point II as a pivot. Arm II carriesa rider ll of soft iron or other magnetic material that moves between two stationary magnet contacts II, II.

The transfer switch II also includes a pair of pusher arms 22, 22 in the form of bell crank levers which throw arm II from one to the other of contacts II, II in timed relation with the operation'of solenoids I4, I4. Accordingly. one end of eachlever i2. 22 is provided with a pin 23, 23' which projects into the path of and angages contactor arm I'I while the other ends I4. 24 of each lever are so deposed as to be acted upon by the armatures II. II respectively of solenoids I4 and I4 when their windings II, II are energized.

,Beginning with one side of battery II, the elec trical wiring of the instrument includes a con-- connected t the other side of battery 2| as Isalso conductor 84 to contactor arm ll of the transfer switch II.

It will now be evident that the pointers I, I.

their cooperating stationary contacts I, I, solenoids I4, I4 and transfer switch II are electrically and mechanically cross connected In such manner that whenever the pointer that is "free" is attracted to its associated magnet contact by reason of a change in control through its assoor instrument pointer I that rider I will be drawn into engagement with contact I at a selected and relatively high magnitude of control current in coil 4.

While the drawing shows riders I, I as being of magnetic material and stationary contacts 1, I as magnet bodies, it will be understood that the same desired magnetic attraction can be obtained when the parts are reversed. Further, while it" is preferred to use riders I,'I and contacts l, I' also as current carrying bodies, separate contacts for control circuit current only could be used.

Coils 4, 4' may be connected in series as shown to the source of control current that determines the operation of the load circuit as will be hereinafter explained, or they may be connected in other ways such as in parallel.

The functional arrangement of the parts in the low" and "high" instrument mechanisms is elated moving coil, and held there, the other pointer then being held to its magnet contact will be reset" by its pusher arm and hence freed to ready it for the succeeding change in current through its moving coil in a reverse direction. This will be clear from an inspection of Fig. l where the parts are shown with pointer-I held to contact I, both solenoids I4, I4' are deenergized, contactor arm II of transfer switch II is held to magnet contact II and pointer I is moving clockwise in response to control current through moving coil 4' which, at this instant in the control current cycle is on the increase. when this current has increased to the "high" value-preselected for load circuit operation, rider I on contactor arm 'I' will then have moved into the field of attraction of magnet contact I and pulled up, rotating pusher arm I counterclockwise to .reset" the "low" contact pointer I, and also rotating pusher arm 21 clockwise to throw rider III on contactor arm I! from contact I. to contact II. The dimensions of pusher arms I and I! and their spatial positions relative to pointer I and transfer switch arm ii are so chosenthat pointer I is reset in advance of movement of arm ll. As rider ll breaks with contact II, the circuit to coil II is opened and armature it then drops out.

The load circuit will now remain in the enersized" condition until the control current in coil 4 decreases to the selected low" vaue whereupon rider 8 and contact I are drawn into engagement. Coil I! of solenoid I4 is now energized for a brief period, armature it pulls up and rotates pusher arms I and 22' to first reset the pointer 6' and then transfer rider 20 on contactor arm i1 back to engagement with contact it. When pointer I is reset. the load circuit is broken, disconnecting the battery 26 therefrom, and the load circuit and relay then remain in this condition until the control current in coil 4' shall again have risen to the selected high" value at which time rider 6' and contact I again engage and reconnect battery 26 to the load.

Summarizing the operation, increase in control current in coil 4' to a preselected magnitude operates the relay in one direction to connect battery 28, or some other source of power, to the load circuit conductors; the load circuit then remains in the "energized condition'until control current through coil 4 has decreased to a preselected magnitude whereupon the relay again operates, but in the reverse direction to disconnect battery 28 from the load conductors. By means of this improved relay action, cyclic on" and off operation of a load circuit is obtained in accordance with cyclic variation in control current'between selected maximum and minimum magnitudes. The arrangement is positive in action and has the further advantage in that the relay expends no energy except during the brief periods when it operates. Further by transfering the load conductor 32 to the contact I, the load circuit shown or a second load circuit, if desired, could be closed when the control current in coil 4 reaches the selected low value and opened when the current in coil 4' reaches the selected "high" value.

Reference is now made to Fig. 2, in which a diflerent instrument and transfer switch arrangement is used. In this arrangement, separate instruments in different casings are used, and the transfer switch is located externally of the instrument casings. Thus in Fig. 2, it is seen that the resetting solenoids 35, ll actuate only thepusher arms 38, 36 which alternately reset pointers 31 and 31'. The transfer switch for selecting the correct reset mechanism is in the form of an auxiliary relay II, eners ation of which is controlled in accordance with movement of the instrument pointers. In the illustrated embodiment, when current through'coil ll increases and the high contact is made, i. e. engagement between magnetic rider 8! and magnet contact 40', a circuit is completed from battery 41 through pointer 31' and conductors 43, M to reset solenoid 35, the return path from solenoid 35 to the battery being through conductor l5, relay contact 46, blade 41 and conductor ll. When the armature ll of reset solenoid it pulls up, it rotates pusher arm I counterclockwise to reset the "low" pointer 31. The auxiliary power relay ll is also energized from battery 42 upon engagement between rider I! and contact I. over conductors I3 and II, but this relay has a slower operating characteristic than reset solenoids 36, 35' and hence solenoid 35 will have been energized and pointer 31 reset before relay contact 48 and blade 41 are separated to open the circuit to solenoid II.

, to the selected "low" value and rider 1! engages magnet contact 40, reset solenoid II is energized from battery 42 over conductors il, l. relay contact '2, blade 41 and conductor 48 to reset instrument pointer 31. As rider 3. and contact ll separate, solenoid II is deenergized and the load circuit is opened as blade ll and contact 54 separate. Blade II moves to engage contact I and hence close the energizing circuit to solenoid ll at this point whereupon solenoid ii is -"readied for operation as soon as lider 3! and contact ll next engage.

Reference is now made to Fig. 3 wherein the invention is embodied in an instrument relay having but a single moving system comprising coil ll, pointer arm SI of electrically conductive material, and rider 2 of magnetic material. The pointer ii operates between low" and high" stationary contacts 83, 63' of magnetized material in accordance with variation in control current through coil iii.

For resetting pointer arm ii, the instrument is provided with a reset mechanism comprised of inverted T arm 84 pivotally supported at A pair of spaced insulating sleeves 66, it are mounted at the bottom of T arm 64. These extend to either side of pointer 8i and are so related to the pointer that when arm 64 is rocked to the right. it will reset the instrument pointer from the low" contact 83 and when rocked to the left will reset the pointer from the high" contact '3'. Arm M also carries a soft iron rider .1 which, as the arm rocks about its support pivot, is drawn firmly into engagement with either of two magnetized contacts 6! and SI.

Low and "high reset solenoids 6!, l! are included in the instrument. Their armatures are bell cranks II and II which are pivoted at H,

II, and include end pins 12, 12' that are adapted to engage and rock T arm 64 back and forth as the windings of solenoids 8!, 69 are alternately energized.

Wiring of the instrument includes conductors ll, ll between the coil of solenoid I and magnetized contacts 63, 88; conductors II, I. between the coil of solenoid 69' and magnetized contacts I, 8!; a conductor 11 from one side of battery II to pointer Cl; and a conductor II from the other side of battery ll-to reset arm 84.

The load device (not shown) controlled by the relay may be connected thereto by conductors .0, ll if the battery I8 is also to be used as the source of power for the load. It the controlled load circuit is to be independent of the relay battery, the arrangement shown in Fig. 4 may be used in which the load circuit conductors are opened and closed at the set of contacts 01, I. The arrangement in Fig. 4 is like that of Fig. 3

in all other respects and hence need not be described.

Operation of \the Fig. 3 type of instrument from a viewpoint of function is the same as those shown in Figs. 1 and 2 in that the load circuit is placed in one condition as the "low" contact is made by the instrument pointer mechanism and remains in such condition until the "high" contact is made whereupon it is switched to another condition and remains in the latter condition until the "low" contact is again made.

In Fig. 3, the relay is shown in the condition where control current through coil OI is increasing. At this time the load circuit is closed by contact between rider '1 on reset arm 04 and magnetized contact I. When the control current has attained the selected high" magnitude, rider .2 on pointer 0| will be drawn into engagement with contact I. This completes the circuit from battery II to reset solenoid ll causing bell crank armature II to rotate clockwise and rock arm 84 to the left moving it a sufficient distance for the rider .1 to be attracted to magnetized contact 6|. During this movement, insulating sleeve It engages and resets pointer I from the "high" contact 83. Solenoid ll reverts to its deenergized state as rider .1 and contact 8! separate, the load circuit also being opened at this time.

Pointer ii is now held away from contact I, but upon a decrease in control current to the selected low" value the pointer is then drawn into engagement with the low magnet contact I. When this occurs, reset solenoid I is then momentarily energized to reset pointer 8i, rock arm 64 to the right hand position and again close the load circuit which will remain in this condition until the control current through coil ll is again sufficient to move pointer ii far enough to the right so that engagement between rider '2 and contact 0' again occurs.

In conclusion, it will be evident that the several illustrated embodiments of the invention are indicative of a wide latitude of possible arrangements. Hence it is to be understood that the invention is not to be restricted to the specific embodiments shown, and that various changes may be made by those skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

I claim:

1. A control device comprising an instrument adapted to respond to control current, said instrument having movable contact means adapted to move into engagement with separate stationary contact means at predetermined low and high values of control current respectively, said movable and stationary contacts being mutually magnetically attractive to assure firm engagement therebetween, a pair of solenoids. a pair of pusher arms, each said arm being controlled by one of said solenoids to separate said movable contact means from one of said stationary contact means, atwo-position transfer switch including a blade contact movable between spaced stationary contacts, an energizing circuit for each solenoid including an instrument switch comprising said movable contact means and one of said stationary contact means, each energizing circuit also including the blade contact and one of the stationary contacts of said transfer switch, and means actuating said transfer switch to alternate positions to open the circuit of the last energized solenoid and to close its blade means upon the stationary contact thereof in the circuit of the other solenoid.

2. A control device as defined in claim 1 wherein said transfer switch actuating means comprises additional pusher arms actuated by solenoid.

8. A control device as defined in claim 1 wherein said transfer switch includes load circuit contacts and the switch actuating means comprises a solenoid energized upon engagement between the movable contact means of said instrument and one of its associated stationary contact means.

4. A relay system comprising a pair of relays for measuring the value of a factor, one relay having magnetic contacts adapted to close when the measured value exceeds a predetermined value and the other relay having magnetic contacts adapted to close when the measured value falls below a predetermined value. a solenoid for each relay, pusher means actuated by each solenoid to separate the contacts of its associated relay, an energizing circuit for each solenoid, the circuit for one solenoid being completed upon engagement of the set of, relay contacts separated by the other solenoid and vice versa. transfer switch means including a transfer switch in each of said circuits, and means actuating said transfer switch means to open the circuit to each solenoid subsequent to operation of the pusher means actuated thereby and to close the transfer switch in the circuit of the other solenoid.

5. A control device comprising an instrument having a pair of moving systems adapted to respond to control current, a set of stationary and movable magnetically attractive contacts associated with each system, the movable contact of one contact set being adapted to be drawn into engagement with its associated stationary contact at a predetermined low value of control current and the movable contact of the other contact set being adapted to be drawn into engagement with its associated stationary contact at a predetermined high value of control current, a pair of alternately energized solenoids, an energizing circuit for each solenoid, the circuit for one solenoid being completed upon engagement of the set of contacts separated by the other solenoid and vice versa, a two position transfer switch, a pair of pusher arms actuated by each solenoid lwhen energized. one arm of each pair being adapted to separate the contacts of one contact set and the other arm being adapted to trip said transfer switch, and means connecting said transfer switch into both said energizing circuits in such manner that when tripped by one solenoid, the energizing circuit to such solenoid is interrupted and a gap in the energiz- -ing circuit to the other solenoid is closed.

8. A control device as defined in claim 5 wherein said transfer switch comprises a pivotally mounted switch arm rocked to alternate positions by said pusher arms, and said switch arm carries a contact movable between stationary contacts, said contacts being magnetized to assure firm engagement therebetween.

7. A control device comprising an instrument having a pair of moving systems adapted to respond to control current, a set of stationary and movable magnetically attractive contacts associated with each system, the movable contact of one contact set being adapted to be drawn into engagement with its associated stationary contact at a predetermined low value of control current and the movable contact of the other contact set being adapted to be drawn into engagement with its associated stationary contact at a predetermined high value of control current,

a pair of alternately energized solenoids, pusher means actuated by each solenoid to separate the contacts of the associated contact set, an energizing circuit for each solenoid, the circuit for one solenoid being completed upon engagement of the set of contacts separated by the other solenoid and vice versa, and a solenoid opera-ted combined transfer and load circuit switch having its operating coil connected in one of said solenoid energizing circuits, said switch including load circuit contacts and a second set of contacts controlling switching gaps in the respective solenoid energizing circuits and arranged upon actuation of the switch to open the energizing circuit to the solenoid last energized and to close a gap in the circuit to the solenoid next to be energized.

8. A control device comprising an instrument having a pointer carrying a contact and movable between a pair of stationary contacts, said pointer and stationary contacts being mutually attractive magnetically to insure firm engagement therebetween, a pair of solenoids, a pair of pusher arms, each said arm being actuated by one of the solenoids to effect separation of the contact on said pointer from one of said stationary contacts, a two-position transfer switch, and an energizing circuit for each solenoid, each said circuit being completed through said transfer switch upon engagement between the contact on said pointer and one of said stationary contacts, and said transfer switch being actuated to alternate positions by said pusher arms to open the circuit of each solenoid upon separation of the contacts whose engagement completed the circuit to that solenoid and close a switching gap in the energizing circuit of the other solenoid.

9. A control device comprising an instrument having a pointer carrying a contact and movable between a pair of stationary contacts, said 4D 10 pointer and stationary contacts being mutually attractive magnetically to insure firm engagement therebetween, a rocker arm, said arm being pivotally mounted at one end and including a pair of spaced pins at the other end projecting into the path of movement of said pointer on each side thereof, a pair of pushers actuated respectively by said solenoids to rock said am in opposite directions and separate the contacts on said pointer from each of the respective stationary contactsra two-position transfer switch, and an energizing circuit for each said solenoid, each said circuit being completed through said transfer switch upon engagement between the contact on said pointer and one of said stationary contacts. and said transferswitch being actuated to alternate positions by said pusher arms to open the circuit of each solenoid upon separation of the contacts whose engagement completed the circuit to that solenoid and to close a switching gap in the energizing circuit of the other solenoid.

10. A control device as defined in claim 9 wherein said transfer switch comprises a contact on said rocker arm movable between a pair of stationary contacts, and the energizing circuit to each solenoid is connected through the movable switch contact and one of the stationary switch contacts.

11. A control device as defined in claim 9 wherein said transfer switch comprises a contact on said rocker arm movable between a pair of stationary contacts, and the energizing circuit to each solenoid is connected through the movable switch contact and one of the stationary switch contacts, said movable and stationary switch contacts being mutually attractive magnetically to assure firm engagement therebetween.

ELMER G. DE MO'I'I. 

